The invention discloses an oligomeric phosphate compound, belonging to the technical field of novel compounds. The oligomeric phosphate compound is prepared by the following steps of: reacting triethyl phosphate, tris(2-chloroethyl) phosphate and C1-C12 aliphatic alcohol as raw materials under the action of a catalyst for 2-24 hours at 100-210 DEG C, then removing excessive raw materials in the system to obtain a crude product, and finally, adding an epoxy compound to remove acid in the crude product, thereby, obtaining a final product. The compound has certain degree of polymerization, so that saturated vapor pressure of the compound is reduced; the compound has the advantages of being non-volatile, having low mobility, and the like; meanwhile, the compound also has excellent performances of being efficiently flame retardant, environment-friendly, and the like, so that the compound is a perfect polyurethane foam flame retardant, and can solve a lot of pressure and problems currently facing of polyurethane flame retardants.